Research on scientists'understanding of the workings of building blocks of

Tag : carbon
As well as shedding light on the characteristics of human-madenanomaterials, researchers note that such properties are relevantto the workings of biological structures and phenomena which alsofunction at nano-scales.
The team of scientists, led by Yue Wu, Ph.D., professor of physicsin the UNC College of Arts and Sciences, examined carbon nanotubesmeasuring just 1.4 nanometers in diameter (one nanometer is abillionth of a meter). The seamless cylinders were made from rolledup graphene sheets, the exfoliated layer of graphite.
"Normally, graphene is hydrophobic, or 'water hating' –it repels water in the same way that drops of dew will roll off alotus leaf," said Wu. "But we found that in the extremelylimited space inside these tubes, the structure of water changes,and that it's possible to change the relationship between thegraphene and the liquid to hydrophilic or 'water-liking'."
The UNC team did this by making the tubes colder. Using nuclearmagnetic resonance – similar to the technology used inadvanced medical MRI scanners – they found that at about roomtemperature (22 degrees centigrade), the interiors of carbonnanotubes take in water only reluctantly.
However, when the tubes were cooled to 8 degrees, water easily wentinside. Wu said this shows that it is possible for water innano-confined regions – either human-made or natural –to take on different structures and properties depending on thesize of the confined region and the temperature.
In terms of potential practical applications, Wu suggested furtherresearch along these lines could impact the design of high-techdevices (for example, nano-fluidic chips that act as microscopiclaboratories), microporous sorbent materials such as activatedcarbon used in water filters, gas masks, and permeable membranes.
"It may be that by exploiting this hydrophobic-hydrophilictransition, it might be possible to use changes in temperature as akind of 'on-off' switch, changing the stickiness of water throughnano-channels, and controlling fluid flow."
Wu also noted that this research relates to scientists'understanding of the workings of many building blocks of life (suchas proteins, whose structures also have nano-confined hydrophobicregions) and how their interaction with water plays a role in howthey function. For example, such interactions play an importantrole in the process known as "protein folding," whichdetermines a protein's eventual shape and characteristics.Misfolded proteins are believed to be a cause of severalneurodegenerative and other diseases.
"We don't fully understand the mechanisms behind proteinunfolding upon cooling," Wu said. "Could this kind ofcooling-induced hydrophobic-hydrophilic transition play a role? Wedon't know but it's worth investigating."
Along with Wu, the other study authors were graduate studentHai-Jing Wang, postdoctoral research associate Xue-Kui Xi, Ph.D.,and research professor Alfred Kleinhammes, Ph.D., all from UNC.